Machines capable of delivering a pitched ball are well known in the art. U.S. Pat. No. 4,860,717 discloses a portable ball throwing machine utilizing a lever arm to throw the ball.
U.S. Pat. No. 3,807,379 discloses a spring type ball projecting device which can be programmed to vary the type of delivery. U.S. Pat. No. 4,844,458 discloses a tennis ball serving machine having panning capability. U.S. Pat. No. 5,012,790 discloses a ball throwing machine utilizing a single tire.
Improved versions of baseball throwing machines utilize counter rotating wheels to give velocity, direction and spin to the thrown ball. These machines are, generally, either of the two or three wheel type.
U.S. Pat. Nos. 4,197,827, 4,655,190 and 4,760,835 disclose ball throwing machines of the two-wheel type. U.S. Pat. No. 4,442,823 discloses a ball throwing machine of the three-wheel type utilizing a complex computer control. U.S. Pat. No. 4,712,534 discloses a ball throwing machine having two separate pairs of throwing wheels, each pair being at right angles to the other, one having the axis of rotation in the vertical position and the other having the axis of rotation in the horizontal position. U.S. Pat. No. 5,125,653 discloses a computer controlled tennis serving machine of the two-wheel type.
Although these devices are effective for the purpose intended, they are difficult to control when producing a variety of different pitches (i.e., slider, drop, curve, etc.) that may be utilized under game conditions.
As the aforementioned patents illustrate, the prior art has seen the development of a wide variety of types of apparatuses for reproducing the flight of a ball--as thrown by the human hand or as hit by a baseball bat, tennis racquet or other accessory. From the earliest pitches in the game of baseball, observers have studied the paths of balls thrown by the human hand, arm and body. Such observations are steeped in controversy. The physics of ball flight, however, require that a ball leave a point of projection, at an initial height from the ground, with a velocity in a given direction and with a given spin rotation about an axis oriented in space, fly through space acted upon by air (through which it travels) and be subject to gravity. It has long been the objective to duplicate these variables by mechanical means.